A rectal suppository has the following benefits: the possibility of dosing with a relatively larger amount of drug than that by the oral or injection route, avoiding of disorders of digestion, safety in comparison with injection, avoiding of the decomposition and metabolism in comparison with oral administration, absence of an effect on feeding, expectation of continuous treatment before and during sleep, the possibility of dosing to children and elderly patients who have difficulty in swallowing or who have difficulty in receiving injection, absence of the necessity for a doctor or nurse for administration such as received for injection and the suitability for home therapy. Based on the features descrived above, many rectal suppositories have recently been used for systemic and local therapy in clinical and home treatment.
It has been shown that 6-amino-5-chloro-1-isopropyl-2-(4-methyl-1-piperazinyl) benzimidazole (I) (hereinafter referred to briefly as benzimidazole derivative (I)) which has serotonin.sub.3 antagonistic activity, is effective in inhibiting vomiting caused by the administration of chemotherapy such as cisplatin (Japanese Patent Unexamined Publication No. 17449/1993). Furthermore, benzimidazole derivative (I) is already known to be an effective ingredient as a remedy for irritable bowel syndrome based on serotonin.sub.3 antagonistic activity (Japanese Patent Unexamined Publication No. 145152/1994).
In the Patent Publications cited above, it has been described that said compound has been formulated into injectable and oral dosage forms such as tablets, granules, etc.
However, said oral dosage form is unsuitable because of the difficulty in administering to patients who have difficulty in swallowing due to vomiting, etc. Futhermore said injection is unsuitable because of pain caused by the multiple administration, and is also inappropriate for home therapy.
In Japanese Patent Unexamined Publication No.48258/1995, percutaneous dosage forms such as the patch and ointment comprising the benzimidazole derivative (I) as the active ingredient having serotonin.sub.3 antagonistic activity have been disclosed. However, the suppository comprising the benzimidazole derivative (I) as the active ingredient is unknown.